One day in 1946, he was experimenting with a magnetron, an electronic device that emits microwaves. While sitting next to the magnetron, Spencer felt a warm, moist sensation in his pocket - a peanut snack bar had melted. Immediately, he realised that microwaves might have the potential to cook food. He sent for some popcorn kernels, placed them next to the magnetron, and then watched as they popped. The next day he experimented with an egg, which began to quiver as the heat and pressure built up inside. When a colleague leant forward to take a closer look, there was an explosion, and he literally ended up with egg on his face. The first commercial microwave oven was sold just one year later.
Microwaves have continued to have a serendipitous history, as illustrated by the story of the British engineer Bill Lucas, who made the fortuitous mistake of letting his tea go cold. He popped his cup in the microwave, with cat-astrophic results. Sparks danced wildly around the cup, because it had a gold rim. As most people know, you should never put metal in a microwave oven, since the sparking can be dangerous to the user and damaging to the oven.
Lucas worked at The Welding Institute near Cambridge, and wondered if the sparks that he had witnessed could be harnessed for welding. Metal effectively focuses microwaves, just as a glass lens focuses light, and it was not long before he had constructed a microwave welding machine. The advantage of his prototype was the machine's efficiency, because just as microwave cookers use less energy than conventional cookers, microwave welding seems to use less energy than conventional welding.
I first came across Bill Lucas when he appeared on Tomorrow's World back in 1992, successfully demonstrating his prototype microwave welder live in the studio. Contrary to the popular myth, his invention did not sink without trace, but has since gone from strength to strength. When I spoke to Bill last week, he told me that a German company, Widos, is now manufacturing and selling microwave welding systems.
Simon Singh is the author of 'The Code Book - the Science of Secrecy from Ancient Egypt to Quantum Cryptography', Fourth Estate, pounds 16.99